Duplexer

Abstract

Duplexers for high power applications are disclosed. In some embodiments, a duplexer includes 2N band pass filters, where N is an integer greater than 1. The 2N band pass filters each have an input and an output and are in an electrically parallel configuration. The duplexer includes a first adaptation circuit configured to couple a transmit signal received from a transmitter to each one of the 2N band pass filters. The duplexer includes a second adaptation circuit configured to couple outputs of the 2N band pass filters to an antenna, the second adaptation circuit providing an isolated path between the antenna and a receiver.

What is claimed is: 
     
       1. A duplexer, comprising:
 2N band pass filters, N being an integer greater than 1, the 2N band pass filters each having an input and an output and each having a characteristic impedance of Z 0  ohms, the 2N band pass filters being in an electrically parallel configuration; 
 a first adaptation circuit configured to couple a transmit signal received from a transmitter to each one of the 2N band pass filters, the first adaptation circuit including:
 a first 90° hybrid coupler having at least one input and at least two outputs and configured to couple the transmit signal toward the 2N band pass filters, the first 90° hybrid coupler having an impedance of Z 0 /N ohms; 
 a first quarter-wave transmission line coupled to the at least one input of the first 90° hybrid coupler, the first quarter-wave transmission line having a characteristic impedance of √{square root over ((Z in *Z o )/N)} ohms, where Z in  is an input impedance of the transmitter; and 
 
 a second adaptation circuit configured to couple outputs of the 2N band pass filters to an antenna, the second adaptation circuit providing a reflective path between the antenna and a receiver. 
 
     
     
       2. The duplexer of  claim 1 , wherein the first adaptation circuit further includes a splitter circuit configured to direct an output of the 90° hybrid coupler to each of a plurality of the 2N band pass filters. 
     
     
       3. The duplexer of  claim 2 , wherein the splitter circuit includes a first splitter having N output ports and a second splitter having N output ports, each splitter receiving as an input an output of the first 90° hybrid coupler. 
     
     
       4. The duplexer of  claim 1 , wherein the second adaptation circuit includes a second 90° hybrid coupler configured to receive outputs of the 2N band pass filters, and to couple the received outputs to the antenna. 
     
     
       5. The duplexer of  claim 4 , wherein the second adaptation circuit includes a combiner circuit having a plurality of input ports, each input port receiving an output of one of a plurality of the 2N band pass filters. 
     
     
       6. The duplexer of  claim 5 , wherein the first combiner circuit includes a first combiner having N input ports coupled to a first set of N output ports of the 2N band pass filters. 
     
     
       7. The duplexer of  claim 6 , wherein the first combiner circuit includes a second combiner having N input ports coupled to a second set of N output ports of the 2N band pass filter. 
     
     
       8. The duplexer of  claim 1 , wherein the band pass filters are acoustic wave band pass filters. 
     
     
       9. The duplexer of  claim 1 , wherein the band pass filters are low temperature co-fired ceramic, LTCC, filters. 
     
     
       10. A duplexer configured to couple a transmitter to an antenna, and to couple the antenna to a receiver, the duplexer comprising:
 2N band pass filters, N being an integer greater than 1, the 2N band pass filters each having an input and an output and each having a characteristic impedance of Z 0 , the 2N band pass filters being in an electrically parallel configuration; 
 a first adaptation circuit configured to couple the transmitter to each one of the 2N band pass filters, the first adaptation circuit comprising:
 a first 90° hybrid coupler having at least one input and at least two outputs, the first 90° hybrid coupler having an impedance of Z 0 /N; 
 a first quarter-wave transmission line coupled to the at least one input of the first 90° hybrid coupler, the first quarter-wave transmission line having a characteristic impedance of √{square root over ((Z in *Z 0 )/N)}, where Z in  is an input impedance of the transmitter; 
 a first splitter having an input and N outputs, the input of the first splitter being coupled to a first one of the at least two outputs of the first 90° hybrid coupler, and the N outputs of the first splitter being coupled to the inputs of a first set of N of the 2N band pass filters; and 
 a second splitter having an input and N outputs, the input of the second splitter being coupled to a second one of the at least two outputs of the first 90° hybrid coupler, and the N outputs of the second splitter being coupled to the inputs of a second set of N of the 2N band pass filters; and 
 
 a second adaptation circuit configured to couple each one the 2N band pass filters to the antenna, the second adaptation circuit configured to provide a reflective path between the antenna and the receiver, the second adaptation circuit comprising:
 a second 90° hybrid coupler having at least two inputs and at least two outputs, the second 90° hybrid coupler having an impedance of Z 0 /N; 
 a second quarter-wave transmission line coupled to a first one of the at least two outputs of the second 90° hybrid coupler, the second quarter-wave transmission line having a characteristic impedance of √{square root over ((Z in *Z l1 )/N)}, where Z l1  is a load impedance of the antenna; 
 a third quarter-wave transmission line coupled to a second one of the at least two outputs of the second 90° hybrid coupler, the third quarter-wave transmission line having a characteristic impedance of √{square root over ((Z in *Z l2 )/N)}, where Z l2  is a load impedance of the receiver; 
 a first combiner having N inputs and an output, the N inputs of the first combiner being coupled to the outputs of the first set of N of the 2N band pass filters, and the output of the first combiner being coupled to a first one of the at least two inputs of the second 90° hybrid coupler; and 
 a second combiner having N inputs and an output, the N inputs of the second combiner being coupled to the outputs of the second set of N of the 2N band pass filters, and the output of the second combiner being coupled to a second one of the at least two inputs of the second 90° hybrid coupler. 
 
 
     
     
       11. The duplexer of  claim 10 , wherein the band pass filters are acoustic wave band pass filters. 
     
     
       12. The duplexer of  claim 10 , wherein the band pass filters are low temperature co-fired ceramic, LTCC, filters.